1. Field of the Invention
The present invention relates generally to a wireless packet data system, and in particular, to an apparatus and method for managing a location of a packet call in a radio environment.
2. Description of the Related Art
In general, a wireless packet data system is included in a mobile communication system, and refers to a system for transmitting data in the form of a packet through a wireless network. For example, the system includes a CDMA (Code Division Multiple Access) system, a PCS (Personal Communications Services) system and a future mobile communication system such as a CDMA-2000 system and a W-CDMA system, standardisations of which are under way.
Meanwhile, the wireless packet data system manages information pertaining to a mobile in service in order to provide a packet call service. Here, since the “mobile” refers to a mobile station (MS) not a base station (BS), the information on the mobile must necessarily include location information of the mobile. Further, a base station controller (BSC) constituting the wireless packet data system processes packet data incoming to and outgoing from the mobile according to the managed location information of the mobile.
The location information is managed in different ways according to states of the mobile. In an active state and a control hold state where certain channels are established, the location information is managed through a handover. That is, since the mobile performs a handover using a dedicated signaling channel (dsch), a dedicated traffic channel (dtch) and a dedicated MAC (Medium Access Control) channel (dmch), it makes the transition from one state to another state while maintaining one or more channels to the BSC during a handover. Accordingly, the movement of the mobile in the above states can be continuously traced by the BSC.
However, if the mobile enters a dormant state where transmission and reception of the traffic is not performed because no packet data is transmitted for a predetermined time, there exists no connection between the mobile and the BSC, making it impossible to manage the location in the same way as done in the active state and the control hold state.
The dormant state means a state where such traffic as voice and packet data is not generated in a state where a radio channel is established. When the dormant state occurs, the wireless packet data system manages a location of the packet call in the dormant state to prepare for later resumption of the traffic. For this reason, the conventional wireless packet data system proposes the following four plans of managing a packet call in the dormant state, and adopts one of them.
In a first proposed plan, a home location register (HLR) and a visitor location register (VLR) take exclusive charge of the location management of a call, and a base station system (BSS) deletes all information on a call that entered the dormant state. In this case, when a packet call in the dormant state requests transmission of the packet data, the same process as a normal new call setup process is performed. That is, an initial call setup process, a registration process and an authentication process are all performed. As a result, an exchange of radio messages due to the call setup process increases a load on an RF (Radio Frequency) stage, and brings about processing loads on the VLR/HLR/AC (Authentication Center) due to the registration and authentication processes. In addition, performing the complicated call setup process causes an increase in a packet buffering time, thus increasing a delay time. In particular, it is difficult to trace a location of the mobile existing in the dormant state, so that a paging load may increase when there is a request for an incoming call to the mobile from the network.
A second proposed plan is to compensate the first proposed plan. This plan provides a plurality of the VLRs/HLRs in order to decrease the processing loads of the single VLR/HLR performing the location management. In this plan, location management of the mobiles is not processed in the single VLR/HLR, but the mobility of all the mobiles is processed by a plurality of the VLRs/HLRs on a load shared basis. Therefore, the BSCs determine the VLR/HLR managing the location information of the corresponding mobile using an identifier (ID) of the mobile, and then acquire the mobile information through the corresponding VLR/HLR. However, as the second plan is fundamentally performed in the same procedure as the first plan, the second plan is somewhat effective in decreasing the load on the VLR/HLR but still has the other disadvantages.
A third proposed plan stores an ID of a source BSC initially accessed by the mobile for a packet data service until the call is released, and performs location management and dormant state management of the corresponding mobile by utilizing the stored information. That is, when the mobile is activated in the dormant state, the mobile provides the ID of the initially accessed BSC (source BSC) to a newly accessed BSC (hereinafter, referred to a “target BSC”). In this case, when processing a registration message of the mobile, the target BSC can rapidly access a dormant state database (DB) of the mobile whose packet service is activated. However, to this end, the radio interface standard must be changed undesirably. That is, the message format must be changed such that the mobile can transmit the ID of the source BSC to the target BSC.
A fourth proposed plan is to construct a small-scale VLR not unlike the VLR/HLR connected to a mobile switching center (MSC), and arrange the small-scale VLR in a network where a new server exclusively manages the dormant state of the mobiles. This small-scale VLR is constructed as a BSC. That is, the small-scale VLR is arranged in a network where a separate server is constructed as a BSC, and the BSCs acquire and update the information on the data service call in the dormant state from the separate server. In this case though, it is necessary to construct separate hardware, and guarantee the VLR/HLR-level safety to the new device. In addition, from a viewpoint of the BSCs, there exists an overhead that the BSCs should simultaneously register all the registration messages in the MSC and the separate server as well.